1. Field of the Invention
The present invention relates to a bolt attaching and detaching device for fastening and loosening a bolt, such as a turbine casing bolt of steam turbine while the bolt is being heated by a bolt heater.
2. Description of the Prior Art
In the prior art, a fastening and loosening work of a turbine casing bolt of steam turbine as one example is done such that a bolt heater is inserted into a central hole bored in the turbine casing bolt so as to heat the turbine casing bolt for elongation thereof by a thermal expansion.
That is, in case of a fastening work of the turbine casing bolt, while a nut is being fastened continuously corresponding to the elongation of the turbine casing bolt, rotating angle of the nut is watched and upon confirming that the nut has been rotated by a predetermined angle, then the heating is stopped. Or, an elongation indicator fitted to an end of the turbine casing bolt is watched continuously by an operator and when the elongation of the turbine casing bolt has reached to a predetermined elongation by the thermal expansion, the nut is fastened rotationally by use of a spanner etc. and then a power source for heating is cut.
Also, in case of a loosening work of the turbine casing bolt, while an operator is trying to rotate the nut of the turbine casing bolt with a spanner to confirm the loosening thereof, the turbine casing bolt is heated and when the nut starts to be loosened, the nut is further loosened with several rotations more and then the power source is cut.
In the prior art as mentioned above, there has been a need that an operator attends always and tries to rotate the nut with a spanner while the bolt is being heated. Also, there has been a fear of deterioration of the bolt if the bolt is heated excessively with a negligence of watching of the operator.